Abstract:
This is Version 1.0 of a satellite-derived surface solar energy data set formulated for the Renewable Energy Industry. It contains 52 monthly-averaged parameters, specified by the DOE National Renewable Energy Laboratory, which are useful in the application of solar energy technologies. The Surface Solar Energy (SSE) data set was created by the NASA Langley Research Center and Analytical Services ... and Materials, Inc. under sponsorship of the NASA Mission to Planet Earth program.

This SSE data set is a synthesis of the World Climate Research Program/Surface Radiation Budget (WCRP/SRB) shortwave data set (Version 1.1), ISCCP-C1 (International Satellite Cloud Climatology Project) 3-hourly satellite data, and ISCCP-C2 monthly mean cloud fraction data. ISCCP provides global coverage of satellite data on an equal-area grid (6596 cells). Each cell represents an area equal to that of a 2.5 degree latitude/longitude cell at the equator (approximately 280 square km). Comparison with data from approximately 500 ground sites suggest that the satellite-derived values are generally within 10 percent of surface measured values for most regions of the world. However, there are two notable exceptions.

1. These Version 1.0 values may be as much as 30 percent high in regions of large-scale biomass burning in those months when total precipitation is less than 24mm. These regions are mostly in Africa and South America; however, other parts of the world may be affected to a lesser degree. The error is caused by the fact that the Version 1.1 WCRP/SRB data set did not account for high levels of smoke in the atmospheric aerosols. The full extent of biomass burning and its effect on surface solar energy is not yet known by the scientific community. Efforts are underway at NASA Langley Research Center to correct this problem. It is planned that a Version 2.0 SSE global data set will be available during 1998 which accounts for the majority of the effects of biomass burning.

2. These Version 1.0 values may be as much as 40 percent low over bare snow or ice surfaces. The problem is caused by the fact that the ISCCP C2 data cannot separate clouds from bare snow or ice because of the satellite channels that were used in that product. Comparisons with ground site data suggest that errors are within 10 percent for those snow regions with significant vegetation or topography to cause dark contrast or shadows. Again, it is expected that the future version of this SSE data set will contain more accurate values over snow and ice.

The following parameters will be included for each cell for each of the 12 months. The values for each month will be either the average, minimum, or maximum over the existing SRB data set 4-year period (3 years for January and February). The convention that is used is the following: total irradiance = direct irradiance + diffuse irradiance.

Description:
The RETScreen International Renewable Energy Decision Support Centre seeks to promote the deployment of renewable energy systems by building the capacity of planners, decision-makers and industry to implement more projects successfully. The broad aim of the Centre's partners is to foster increased market uptake of renewable energy technologies (RETs) that reduce the reliance on conventional energy sources and which help to protect the global environment. The Centre builds upon the success of the RETScreen International Renewable Energy Project Analysis Software, which is now being used by more than 21,000 people in 185 countries around the globe and which is growing at 150 new users every week.

The Centre develops enabling tools that allow stakeholders to better analyse the technical and financial viability of possible projects. These tools make it easier for people to consider renewable energy projects at the critically important initial planning stage while significantly reducing the costs of assessing potential projects. Some of the enabling tools include renewable energy project analysis software models and manuals; international product and weather databases; project case studies; and university textbooks. Given the broad aim of the Centre's partners, the Centre provides these valuable enabling tools free-of-charge to users around the globe via the Internet and CD-ROM.